Leonard Tunnel Restoration – Millimeter Precision beneath the Brussels Ring

What was the challenge?
Two supports of the upper tunnel had been severely damaged after years of exposure to rainwater. These had to be replaced. But before that could happen, the weight of the tunnel first needed to be safely transferred — and that’s where we came in.

2,000 tons, spread over two nights
We designed and built two temporary jacking structures inside the lower tunnel. Each construction was capable of carrying 1,000 tons. With these, we carefully lifted the upper tunnel — controlled down to tenths of a millimeter. The risk of cracking was real, which meant absolute precision and control were essential.

A tailor-made solution
The space in the lower tunnel was extremely limited. Together with Rijnstaal and Jan de Nul, we developed a custom fastening system. A bespoke steel construction, combined with prefab concrete components, formed the base. On top of this, we installed our flat injection jacks — specially chosen because they could be mounted by hand. There was no space for cranes or standard lifting setups.

Night work under pressure
All work took place at night. One lane in the lower tunnel was closed each time, while the upper tunnel was temporarily shut down during the lifting. Timing was critical: we only received the assignment two months before Ascension weekend. And since two supports had to be replaced consecutively, the entire temporary structure had to be built up and dismantled twice.

What this says about us
No two projects are the same. But what they often have in common is that standard solutions won’t suffice. Whether it’s lack of space, extreme time pressure, or the need for maximum precision — we adapt, innovate, and deliver. And if that means working underground, at night, in the middle of one of Belgium’s busiest interchanges, then that’s exactly what we do.